1. Field of the Invention
The present invention relates to a transistor whose area is to be reduced.
2. Description of the Related Art
In recent years, downsizing of a gate electrode has been advanced by a technique of slimming, in which a line width is narrowed after the pattern formation using an exposure unit, and the like. Meanwhile, a contact diameter and a distance between a contact hole and a gate electrode are difficult to be reduced to the precision higher than the exposure precision, and in an LSI (Large Scale Integration) on a single-crystalline silicon substrate, downsizing is achieved by a technique of a self-alignment contact and the like. However, when a self-alignment contact technology cannot be employed because of a reason of a process, a design rule that a contact diameter is much larger than a gate length is required to be adopted. The design rule in such a case is, for example, that a contact diameter is approximately 0.2 μm whereas a gate length is 0.065 μm.
On the other hand, a technology for forming an LSI on a glass substrate has been developed recently. The minimum size for processing by a process technology on a glass substrate is much larger than the one by a process technology on a single-crystalline silicon substrate since the glass substrate is larger in area than the single-crystalline silicon substrate and shrink due to heat occurs. In particular, when an organic interlayer film is employed in the case of planarization being required for a display, downsizing of a contact thereof is difficult, and a contact diameter and a distance between a contact hole and a gate electrode are much larger in design rule than a gate length. For example, a design rule that a gate length is 1 μm, a contact diameter is 3 μm, and a distance between a contact hole and a gate electrode is 3 μm is adopted.
In the case of the layout of a transistor according to the above-mentioned design rule, a proportion occupied by a region relating to a contact is increased and downsizing of a design rule of a gate length and the like gives makes few contributions to the reduction in layout area. In such a case, it is most effective for the reduction in layout area to reduce the area of the region relating to the contact.